Alkane sulfonic acid manufacture



Nov. Z9, 1949 w. A. PROELL ALKANB SULFONIC ACID MANUFACTURE Su/fonic Acid INVENTOR. Wayne A. Pros/l 4 TTORNE Y Patented Nov. 29,V 1949 ALKANE SULFONIC ACID MANUFACTUBE Wayne A. Proell.

Chicago, lll., assigner to Stand ard Oil Company, Chicago, Ill., a corporation of Indiana Application December 24, 1947, Serial No. 793,749 16 Claims. (Ciano- 513) This invention relates to an improved process for the production of organic sulfonic acids, particularly those in which the organic radical is a hydrocarbon radical. In applications for United States Letters Patent Serial Numbers 571,023',-

filedJanuary l, 1945, yby W. A. Proell and B. H. Shoemaker and 590,841, iiled April 28, 1945, by W. A. Proell, which have matured respectively into U. S. Letters Patent 2,433,395 and 2,433,396, are described novel processes for the production of organic sulfonic acids, particularly hydrocarbon sul fonic acids such as alkane-sulfonic acids. In the processes of said prior patents the charging stock is a sulfur compound conforming to the general formula RiSnRz. wherein R1 and R2 are organic radicals, e. g. the same or different hydrocarbon radicals, S is sulfur, and n is an integer having a value between 1 and 6, particularly symmetrical or asymmetrical alkyl disuldes. In the processes of said prior patents, said charging stocks are oxidized by a gas containing free oxygen and a catalyst selected from the group consisting' of NO, NO2, N203, N204 and N205, which may be generated in the -reaction zone by nitric acid, which also functions to supply water to the reaction zone. The overall process applied, e. g., to a disulfide conforms to the equation:

although considerable evidence has been obtained that it proceeds through a. rather large number of intermediate oxidation stages .before sulfonic acids are produced.

This application is a C. I. P. of application for Letters Patent, S. N. 590,841 and is directed to an improvement in the processes thereof to yield sulfhonic acids of superior quality by an improved, vreadily controllable operating procedure.

I n the oxidation of a hydrocarbon disulfide, e. g. an alkyl disulde by a gas containing free oxyfgen, e. g. air, in the presence of a catalytic quantity of a nitrogen oxide as mentioned above, oxygen is absorbed rapidly by the reaction mixturef-for a more or less extended initial period, depending on the specific feed stock and operating conditions. The rapid oxidation reaction results vin' the production of 'a mixture of two immiscible liquid phases, viz. sulfonic acid and unconverted hydrocarbon disulde. As the reaction proceeds, the reactivity of the reaction mixture diminishes more or less rapidly as evidenced by reduced rate of oxygen absorption therein. As the oxidation proceeds the sulfonic acid concentration in the reaction mixture increases until a homogeneous mixture or solution of sulfonic 2 acid and hydrocarbon disulfide is formed; at this juncture the reaction mixture is generally characterized by a markedly reduced rate of oxygen absorption compared with the disulfide charging stock. Thus, whereas under a given set of operation conditions (temperature, air rate through the reactor, charge rate through the reactor. pressure), the disulde charging stock will absorb, say, -100% of oxygen from the oxidizing air stream, the solution of-disu1de and sulfonic acid which is produced will, under the same operating conditions.. absorb say, 30-40% of the oxygen from the air stream. Depending upon the charging stock, the formation of the solution may coincide with RSOaH concentrations in the range of about 40-70 weight per cent in the solution.

It is possible in some cases to increase the rate of Oz'absorption of the RzSz-.RSOaH solution by increasing the reaction` temperature to a value above about 70 C., as described and claimed in S. N. 590,841. However, the employment of high temperatures in one or more secondary oxidation stages in most cases results in RSOaH which re-y quires excessive bleaching by concentrated HNO: to produce acid of desirable color and color stability; in fact, the time spent in bleaching such acids `frequent1y exceeds the time required to oxidize B2S: charging stocks to form the crude RSOaH.

However, I have now found that sulfonic acids of superior quality can be produced and coking and corrosion in the reaction zone may be minimized or avoided by maintaining the oxidation reaction temperature below about F'. A1- though at a temperature below about 125 F. the rate of oxygen absorption of RzSz-RSOaH is generally fairly low, over-oxidation of the reaction mixture is avoided with consequent avoidance of the production of darkco1ored sulfonic acids of poor color stability which would require excessive bleaching treatment.

Moreover, the surprising fact has been demonstrated that individual alkyl disuliides such as methyl and ethyl disuldes are, upon oxidation with oxygen-containing gas and a nitrogen oxide catalyst, far more sensitive to temperatures above about 125 F. than a mixture of alkyl dis'ulfdes having about 2 to S'carbon atoms in the molecule obtained by catalytic. oxidation of the correspending mercaptans obtainable from petroleum naphtha by extraction with caustic solutions (the so-called Solutizer process). When said oxidaandere H2504, H2O and ash contents and therefore was fit only for certain low grade commercial uiteenl However, by the low temperature process (not in 5 product was otherwise undesirable in having high i Although charging stocks conforming to the general formula RiSnRz (supra) can be employed.

the process will be described in its application to hydrocarbon disuldes such as alkyl disuldes. Suitable charging stocks are individual alkyl disulildes or mixtures thereof. Preferred alkyl dlsulfldes contain at least one primary or secondary alkyl group. Properties of representative alkyl disulfide charging stocks are set forth in Table I excess of 125 F.) herein described and claimed A10 below.

Table I A. S. T. M. Distillation, F. Reid nimma sp. or. 1211;

Initial 10% 30% 50% 70% .90% Max. sure Methyl 225 226 227 227 228 229 298 1.050 Ethyl 298 304 304 305 305 305 312 1.005 0.7 Mixedl 267 28B 300 307 3l 328 355 0.990 0.3

l A mixture oi symmetrical and asymmetril alkyl disuiildes having 2 to 7 carbon atoms, inclusive, in the molecule; obtained by steam distillation of disulildes derived from caustic extraction of a petroleum naphtha followed by oxidation oi the caustic extract. This mixture is essentially free of napbtha, phenolic materials and polyeulildes. The average m. wt. is about. 122, corresponding to it has been possible for the rst time to produce 2 commercially desirable individual alkanesulfonic acids such as methaneand ethane-sulfonic acids having light color, good color stability; low H2O. HzSOl, and low ash contents, in equipment exceeding laboratory scale, viz. in a reactor of 1 3 cubic foot capacity.

In a small-scale (laboratory) vertical oxidation tower I have found it feasible to counterow liquid disulfide charging stock downwardly against anl air stream containing a nitrogen oxide catalyst. 35

However when this method was tested in a larger reaction tower having a volume of about 1 cubic foot, seemingly insuperable dilcultles were en4 countered which resulted in the abandonment of the tower oxidation method and in the alternative A40 and less desirable use of kettles or autoclaves. i These difficulties were, in the main, lack of adequate temperature control which in turn resulted in coking and corrosion of the reaction towerand discoloration and deterioration of the RSOaI-I '45 product, and iiooding of the reaction tower. These difficulties in the tower oxidationxmethod appearedv insuperable until concurrentv downflow of liquid disulfide charging stock oxidizing gas and nitro; gen oxide catalyst through the tower was found Y to result in their substantial elimination. Ther most practical and unexpectedly eifectiv'e method.'

v therefore, of operating the low temperature (notin excess of 125 F.) oxidation process of the present invention is the concurrent downilow method just described. Although the low temperature j oxidation process of the present invention mayv also be eifected in autoclaves, pipe coils, etc., lijf, should be emphasized that by the employment of downiiow concurrent contacting of gas and liquid in the reactor and by not allowing the reaction temperature to exceed about 125 the oxidation operation has been transformed from an erratic operation requiring strict supervision and sensi- 6 tive control, to a relatively simple operation requiring a minimum of operating skill and far less stringent supervision. The tendency toward run'- away temperatures (which may lead to ignition) is avoided by use of concurrent ilow.

In order to describe the present invention with more particularity, reference is made at this point to the gure, which is a schematic ilow diagram indicating suitable reaction equipment for effecting tLe present process.

Etabr.

The oxidizing agent employed in the present process is a gas containing free oxygen. Commercially, air is the preferred oxidizing agent, but other gases containing free Ozmay be employed. such as kflue gases containing O2, Oz-enriched air, etc.

The oxidation catalyst is a nitrogen oxide as described above. ylin general, it is necessary to inf troduce with the feed stock less than 10% by weight of nitrogen oxides based on the total oxygen absorption, and usually I introduce about 1 to about 5% by weight of nitrogen oxide based on the oxygen consumed.

commercially, it is preferred to employ nitric acid as a source of nitrogen oxide catalyst. Nitric acid, thus employed, serves also as a Source of water required for the production of RSOzH, asA indicated by the equation (supra). A nitrogen oxide such as NO2, 70 weight per cent nitric acid' and 91 weight per cent nitric acid have been employed in the present oxidation process, indicating that the nitric acid concentration is not of critical importance. Two factors' determine th desirable catalyst rate: (1) The amount of nitric acid in the liquid reactants should be suilicient to promote rapid absorption and utilization of oxygen; (2) the nitric acid concentration must be above a certain minimum to prevent corrosion of steel and other metal parts in the reaction equipment. Rapid attack of 18-8 stainless steel reaction equipment has been observed when the reducing capacity of the disulfide charging stock has been in excess of the oxidation capacity of the amount of O: and nitrogen oxide catalyst. It has been observed that the concentration of nitric acid necessary to insure smooth oxidation of akyl disulde charging stocks is greater than the amount needed for corrosion protection of steel reaction equipment.

As has been pointed out above, water is a. nec--y essary reactant for the production of sulfonic acids from disulfldes. or for that matter from polysulfides. It has been observed that even when the oxidation of an'allnyl disulfide is ef- 75.8111101116 anhydrides (S. N. 702,989-W. A. Proell.

e minimum" reaction, but as the reaction proceeds, the reactivity of the material in process diminishes more or less rapidly, resulting in a decrease in oxygen cleanup from the air stream. It has been observed that over 80% of the oxidation reaction may be completed during the initial rapid reaction. When the oxygen cleanup drops to about 3040%, the air rate to the reactor is reduced, the rate of nitric acid injection is maintained to give 2-3 mol per cent HNO; in the entering air, and the reaction is completed by about 20 hours of operation at this rate. The product is ready for final refining operations when the reaction mixture becomes entirely water soluble. It is preferred to hold the reactor tower bottoms temperature at about 95 to about 105 F. throughout the run, except during the initial period of rapid oxidation, when it may reachV about 115 F. to about 120 F. but should not for any substantial length of time exceed a temperature oi' about 125 F. `The liquid circulation rate through the reaction system is desirably maintained constant throughout the run.

A typical crude mixture of alkanesulfonic acids produced by the process just described will con,- tain about 1 to about 3 Weight per cent H2O; about 1.5 to about 3 weight per cent H2SO4; ash in trace amounts to less than about 0.01 weight per cent; are amber. to red in color as contrasted to the black color characteristic oi' crude acids which have been at least partially decomposed by exposure to high temperatures in excess of about 125 F.

Although the alkanesulfonic acids produced directly by the catalytic oxidation process are suitable for many purposes with little'or no refining, it is desirable to practice some refining upon the crude sulfonic acids in order to fit them better for certain specialized uses. To this end, the crude sulfonic acid product iinally separated in drum I8 and having a suli'onic acid concentration of at least about 90 weight per cent, is passed through line 20 and forced by pump 42| through line 22 and heat exchanger 23, thence through line 24 into'valved line 3G. The crude sulfonic acid in line 36 is joined by a stream of fuming nitric acid entering through valved line 3l. Usually, between about 5 andk about 10 weight per cent of about 91 weight per cent nitric acid is slowly added to the crude sulfonic acid` and passed through cooler 38 to avoid local overheating to temperatures higher than about 140: F. Nitric acids having concentrations between' about 60 and about 100 weight per cent may be employed in the refining operation. suitable lquantities being employed to achieve the desired extent of refining.

The mixture of crude sulfonlc acid and HNO: passes into the refining tower 39 at its upper end and passes downwardly over suitable packing material 40 into the bottom of the tower, whence it is recirculated through line 4| and pump 42 through valved line 43 and line '36 to the top of the rening tower. The temperature of the circulating liquid stream is controlled by suitably proportioning its flow through a by-pass heat exchanger 44 in line 43. Rening tower 33 is also provided with an overhead valved vent line 45 containing a knockback condenser 46.

The mixture of crude sulfonic acid and nitric acid is circulated through the refining tower at about 140 F. for 4 hours, maintaining a sumciently high liquid circulation rate through the tower to prevent local overheating. Then the tothe circulating liquid stream and air or other inert gas such as N2, CO2, iue gas, etc. is introduced through valved line 4l into tower 33 to remove nitrogen oxides absorbed in the sulfonic' acid. Suitable stripping temperatures are between about 180 and about 240'F., e. g. 200 F. Stripping of the sulfonic acid is continued until the suli'onic acid product test for nitrates.

In place of the reiining towerillustratd in the gure, it will be evident that an autoclve provided with heat exchange coils could be employed; agitation in such an autoclave could be produced by bubbling air or other inert gas through the liquid or by the use of a mechanical agitator;

If desired, the nitric acid rening procedure may be repeated; it may also be followed by contacting the Vsulionic acid with adsorbents such as charcoal, preferably after dilution of the sul-v fonic acid with water, e. g. to an acid concentration of 35-45 weight per cent.

stainless steei (typesaoz and 304) has proved" satisfactory in service on an oxidation plant as illustrated in the gure, provided care was taken to avoid reducing conditions by providing unin. terrupted ilow of nitric acid catalyst and air into the system before oxidation is complete. It has also been observed that corrosion is prone to occur in locations where liquid stagnates, as in pump seals. Worthite, an alloy steel containing 2325% nickel, 19-2l% chromium, 3% molybdenum, 3.25% silicon, 1.75% copper, .6% manganese, and less than .07% carbon, has exhibited markedly superior corrosion resistance under reducing conditions in contact with a mixture oiallqrl disuliides and alkanesulfonic acids containing 1 to 4 carbon atoms in the molecule at 210 F.

for 17 hours. Under these conditions, WorthiteA was corroded at the rate of 0.006 inch per year, compared e. g. with 2.96 inches per year for type 304 stainless steel.

In Table 2 are presented the operating conditions for a series of batch runs in which various alkyl disulildes were oxidized by concurrent downiiow with air and nitric acid through a vertical Vstainless steel (type 304) reactor having a volume of 1 cubic foot (3.8 inch I. D. by 10' long) packed with 1/2 inch Berl saddles and provided near its upper end with a liquid distributing plate, as shown in the iigure. The remainder of the oxidationv reaction equipment was set up for ilow as shown in the figure. A CaCl: air dryer was employed. The liquid circulation rate through the reactor was maintained substantially constant'at 5 gaL/min.; this circulation rate results in the passage of 3600 gals. per hour per square foot of reactor cross section and usually results in a temperatue rise through the reactor of about 20 Il'. due to the heat liberated by the reaction. Nitric acid (70 weight per cent) was metered into the air stream. During the induction period (approximately 1 hour), the pressure in the oxidation reactor was maintained at about 5 p. s. i. g.; upon the onset of rapid oxygen absorption in the circulating liquid reaction mixture, the pressure was increased to 50 p. s. i. g. The only inten gives a negative FeSO4 I aman in the 70 weight per cent nitric acid employed was maintained for four hours. Then the temas the source of nitrogen oxide catalysts.

persture of the acid was increased to 200 F. 'and Table 3 RnnNo l l s 4 5 nkyl piscina ma sunk sin!! nml Many! wxga l Mixed 'lsmp.1'.:

Mx'atnmmm anuncian mi ich) ma (muni) mii il n n ...L lita m man uma, 2454 --..12 aan -111 as sa.

1 A mixture of alkyl disuliides having the speciiications set forth in 'Poble l.

I Average of temps. at temps. at top and bottom oi l During initial stage oi rapid oxygen absorption.

During secondary stage oi slow oxygen absorption.

l Represents a temerature surge ot short duration; the range oi 90 to 100 Table 3 Bun No l 2 3 4 5 Alkyi disulfide charge..- Ethyl Ethyl Methyl Mixed Mixed Material Balance dhxlilde charge, lbs----. 61.0 80.0 31.3' 64.0 80.0 total oxygen consumed trom air,ibs 41.7 56.6 26.6 28.4 60.0 ter from nitric acid,

ireeand ccmbined.lbs. 6.35 6.27 9.82 6.09 6.16 oxygen from HNO: de-

composition, lbs 1.40 1.38 2.16 1.54 1.36 totaiconsumtiomlbs..- 110.46 144.25 69.88 100.96 147. 62 milonic aci product,

lbs 104.25 12M 60.11) 102.82 135.00 Weight per cont recov- 011cm Consumption total air into reactor, lbs. 343.0 394.0 275.0 332.0 422.0 totsloxygen intoreactor,

lbs 79.0 90.5 63.3 76.4 97.1 total oxygen consumed,

lbs 41.7 56.6 26.6 28.4 $1.0 overall oxygen cleanup,

percent 52.8 60.0 41.0 37.2 61.7

NlbicAcid Consumption nitric acid (70 weight ret cent) consumed,

be 15.8 15.6 24.4 17.4 22.3 overall mol per cent HNOxinenteringair-. 1.6 1.27 2.85 1.68 1.70

Product Analysis Before Bleaching:

water, weight per cent 0.526 0.41 2.85 0.88 HzSOl, weight per cent 1.027 0.96 2.22 1.90 RSOlH, welght per cent 98.9 99.6 93.0 02.21 Ash,weight per cent. 0.01 0.007 0.008 trace After Bleaching:

Water, weight per cent 1.41 1.89 2.99 3.88 3.22 HISO, weight per cent 0.92 1.37 1.85 2.46 2.43 RSOzH, weight per cent 08.4 96.2 92.40 93.40 03.0 Ash,weght per cent. 0.02 0.02 0.02 0.015 0.02 C or,N.P. 11.5 1 1-1.5 2.5 22.5 Color after 3 hrs at 210" F., N. 1.5 1-l. 5 11.5 3 3 The material balances, oxygen consumption, nitric acid consumption and product analyses obtained by the operations summarized in Table 2 reactor through tlie mn.

throughout mbstfnntislly the entire run the temp. was closely coniined to held for six hours. Then about 3 to 5 weight per cent of 91% nitric acid was added and the acids were stripped with air at about 200 F. employing an air rate of 175 S. C. F./hr. until the FeSOs test applied to sulfonic acid samples was negative. Stripping usually occupied from about 20 to 3o hours.

In Table 3, the negative H2O contents of the `crude sulfonic acids produced in runs 1 and 2 in- Y dicate that no free water was present in the sul- .Icnic acid products, but that they reacted with H2O to the extent indicated. The negative H2O values indicate the presence of sulfonic anhydride in the crude reaction products. Thus, the negative water value in run 1 would indicate that the crude ethanesulfonic acid product contains approximately 6 weight per cent oi' ethanesulfonic anhydride.

A water balance on the various runs set forth in Table 3 shows that from 120 to 150 weight per cent of the water charged is recovered as free and chemically combined water in the product. Although less free water than was theoretically required has been added to the reactor during the Y oxidation process, free water has been recovered example, in run 4, the amount oi.' water required in some of the crude sulfonic acid products.. For

by'theory to be added to the reactor is 91.6 lbs. Although only 6.99 lbs. of water were added, the

= crude sulfonic acid product contained 2.85 weight self-explanatory. From the data it will be noted that the process of the present invention renders possible the consistent production of sulfonic acids in high yields. The sulfonic acid products are. moreover, characterized bytheir uniformly low contents oi impurities and by their light color. The retention by the sulfonic acid products of light color after being heated for three hours at 210 F. is evidence of their good. color stability.

In contrast to the rults obtained in the present low-temperature oxidation process, a typical mixed alkanesulfonic acid product derived from a process diiering from that of the invention by employing temperatures above 125 F. to accel-e crate oxidation in the second V(slow oxygen absorption) stage had the following properties:

RSOaH (110 m. w.) weight per cent-- 90 H2804 rin 3 'H2O an 4 Ash do 0.02 Sp. gr. 1.37 Color, N. P. A. 4 Color after 3 hours at 210 F., N. P. A. 7

carried out at atmospheric pressure.

The material balances obtained in runs l to are considered good in view of the relatively small size of-reaction system and in view of some mechanical diiilculties causing leakage from the equipment.

Although certain specific -embodiments of the present invention have been detailed, it should be understood that the inventive concept is'not limited thereto. Thus, although I prefer to conduct the oxidation at temperatures between about 90 F. and about 110F., the oxidation can generally be conducted at temperatures between about 20 F. and about 125 F. With some charging stocks, temperatures as high as about 150 F. may be used, e. g. temperatures in the range of about 50 to about 150 F. Although the oxidation runs described above were conducted at the reactor pressure of 50 p. s. i. g., other runs have been During the initial stages of oxidation in which oxygen is absorbed very rapidly by the liquid reaction mixture,

it is advantageous to maintain a high concentra-v tion of oxygen in the reactor; this may be efected, e. g., by employing air enriched with free oxygen or by employing air or other oxidizing gas stream under pressure. Air enriched to 60% oxygen content has been employed to accelerate the oxidation oi alkyl disulildes at atmospheric pressure; air has also been employed in this process at 75 p. s. i. g. Since, at least during the stage of rapid oxidation, the eil'ect of pressure is to lncrease the rate of oxidation of the charging stock,

the true upper limitation on the pressure at which.

the reaction can be conducted appears to be limited by simply the rate at which heat can be removed from the reaction mixture to prevent its temperature from increasing above about 125 F. Explosionsmay occur if the initial oxidation is conducted under high pressure with air, and it -becomes impossible to remove the heat of reaction at a sumciently rapid rate.

Althoughk the maximum air rate employed in `the rims specifically detailed above was 250 S. C. F./hr.,much higher air rates could probably be employed in a larger reactor or one providedv with suiiicient heat Aremoval means. Since, in

thepresent process, the ilow of liquid and gas through the reactor is concurrently downward,

the danger of reactor flooding at high gas velocitiesis practically eliminated. After the oxidation reaction enters thesecondary stage characterized by slow oxygen obsorption in a one-phase liquid reaction mixture, it is usually desirable to reduce the air rate in order to (l) conserve power, (2) reduce the small amounts of water which enter the reactor with the air stream, (3) reduce a suillclently dry charging stock and a sumciently low amount of water introduced with the catalyst so that during the latter part of the reaction the amount of water present does not substantially exceed 1% by weight based on introduced disulildes. Greater water tolerance is permissible in the initial stages of the oxidation, the limitation of the amount of water of less than about 1% being particularly important after the homogeneous phase conditions are reached. Exceeding this water limit results in a retarded reaction rate. 1

Numerous, variations oi' the inventive process will readily suggest themselves to one skilled ln the art, such as the conversion of the batch process herein decribed to a semi-continuous or continuous basis, etc.

Having thus described my invention, what I claim is:

1. The process for producing a. sulfonic acid which comprises oxidizing a hydrocarbon disuliide by passing said disulfide, a gas containing free oxygen, and a catalytic quantity of a nitrogen oxide selected from the group consisting of N0, N02, N203, N204 and N205, downwardly in concurrent contact through a vertical reaction zone at a temperature not exceeding about 125 F., and continuing the oxidation until more than 90 percent by weight of said disulfide has been oxidized. Y

2. The process of claim 1 which includes the additional steps of removing apartially oxidized product from the lower end of said vertical reactionl zone, cooling said partially oxidized product to an oxidation reaction temperature not in excess of about 90 F. and recycling the cooled partially oxidized product to the upper end of;

said vertical reaction zone.

3. The process for producing an alkanesulfonic acid'which comprises oxidizing a disuliide having the formula R1SSR2 wherein R1 and R2 are de and a gas containing both free oxygen and a catalytic quantity of a nitrogen oxide selected from the group consisting of N0, N02, N202, N204 and N205 downwardly in concurrent contact through a vertical reaction zone at an oxidation reaction temperature.

catalyst removal from the reactor by the partially spent air stream, and (4) increase the residence time of oxygen in the reactor.

One reaction towerhas been depicted in the gure for eilecting the entire oxidation process. However, two or even more reaction towers may be employed. Thus, the rapid oxidation stage can be effected in a reaction tower having in,

ternal or associated heat removal facilities caf pable of rapidly removing large quantities of heat;

the second or slow oxidation stage can be effected in a smaller tower which would not require such extensive heat removal facilities as the first reaction tower'. The first reaction tower would be operated under relatively high superatmospheric pressure, e. g. 50-100 p. s. i. g., whereas the second towerv might be operated at about 0-25 l. s. i. g.

Preferably the reaction should be effected with 4. The process for-producingv a sulfonic acid from an organic sulfur compound having the formula RlSnRz wherein R1 and R2 are hydrocarbon radicals and 11. is an integer having a value'between 1 and 6, which process comprises passing said sulfur compound, a gas containing free oxygen, and a catalytic quantity of a nitrogen oxide selected from the group consisting of N0, N02, N203, N204 and N205, downwardly in concurrent contact through a vertical reaction zone at a temperature not exceeding about 125 F., and continuing the oxidation until more than 90 percent by weight of said sulfur compound has been oxidized'.

5. The 'process for producing a sulfonic acid which comprises passing a hydrocarbon disulilde,

a gas containing free oxygen and a catalytic` quantity of a nitrogen oxide selectedA from the t vsaid sulfur compound, a gas contain oxidized product to a temperature between about 60 F. and about 90 F., recyclingv the cooled, partially oxidized product to the upper end of said vertical reaction zone, and continuing the oxidation until more than 90 percent by weight of said disulfide has been oxidized. y

6. The process for producing an alkanesulfonic acid from a disulfide having the formula RiSSRz wherein R1 and R2 are alkyl radicals having 1 to 6 carbon atoms and at least one of said radicals is selected from the class consisting of primary and secondary radicals, which process comprises passing said disulfide, a gas containing free oxygen and a catalytic quantity of nitric acid downwardly in concurrent contact through a vertical reaction zone at a temperature between about 20 F. and about 125 F., removing a partially oxidized product from the lower end of said vertical reaction zone, cooling said partially oxidized Ysaid sulfur compound, a gas containing free oxygen, and a catalytic quantity of nitric acid downwardly in concurrent contact through a vertical reaction zone at a temperature between about and 125 F., and continuing the oxidation until more than 90 percent by weight of said sulfur compound has been oxidized.

product to a temperature between about 60 F. 20

and about 90 F., recycling the cooled partially oxidized product to the upper end of said vertical reaction zone, and continuing the oxidation until more than 90 percent by weight of said disulfide has been oxidized.

. 2 7. The Yprocess for producing an alkanesulfonic acid from a disulfide having the formula R1SSR2 wherein R1 and Rz are-alkyl radicals having 1 to 6 carbon atoms and at least one of said radicals is selected from the class consisting of primary and secondary radicals,iwhi ch process comprises passing said disulfide, a gas containing free oxygen, water in an amount substantially less `than the amount theoretically required, and a catalytic quantity of nitric acid downwardly in concurrent contact through a vertical reaction zone at a ternperature between about 20 F. and about 125 F.,

`removing a partially oxidized product from the lower end 0f said vertical reaction zone, cooling 11. The process of claim 10 wherein the organic sulfur compound is a hydrocarbon dlsulfide.

l2. The process for producing a sulfonic acid from an organic sulfur compound having the formula RrSnRz wherein R1 and R2 are hydro- 5 carbon radicals and n is an integer having a value between land 6, which process comprises passing said sulfur compound, a gas containing free oxygen, and a catalytic quantity of a nitrogen oxide selected from the group. consisting of said partially oxidized product to a temperature between about 60 F. and about 90 F., recycling the cooled partially oxidized product to the upper end of said vertical reaction zone, and continuing the oxidation untilv more thanV 90 percent by weight of said disulfide has been oxidized.

8. A process for producing an alkanesulfonic acid from a disulfide having the formulaR1SSRz wherein R1 and Rz are alkyl radicals having 1 to 6 carbon atoms and at least one of said radicals is selected from the class consisting of primary and secondary radicals, which process comprises passing said disulfide, a gas containing free oxygen, and a catalytic quantity of a nitrogen oxide selected., from the group consisting of NO, NO2, N203, N204 and'NzOs, downwardly in concurrent contact through a vertical reactionzone at an oxidation reaction temperature not exceeding about 125 F., and maintaining the amount of water present in the reaction mixture below about 1 percent by weight based on disulfide charged to said reaction zone during that portion of the reaction period in which the reaction mixture consists essentially of a homogeneous solu,

tiolri of said disulde and lsaid alkan'esulfoni/ ac 9. The process for producing a sulfonic acid from an' organic sulfur compound having /the formula RiSnRa wherein Ri carbon radicalsand n is an integer having /a/ value between 1 and 6, which process comprises/ passing (ng free and Rz are hydro- N0,N0z, N203, N204 and N205, downwardly in concurrent contact through a vertical reaction zone at an oxidation reaction temperature.

13. The processl ozt` claim 12l wherein the organic sulfur compound is a hydrocarbon di- 1 sulfide.

14. The process of claim'12 which includes the additional steps of removing a partially oxidized product from the lower end of said vertical reaction'zone, cooling said partially oxidized product, and recycling the cooled, partially oxidizedv product to the upper end of said reaction zone.

15. The process of claim 14 wherein the organic sulfur compound is a vhydrocarbon disuliide.

16. The process` for producing an alkanesulfonic acid from a disulfide having the formula R1SSR2 wherein R1 and R2 are alkyl radicals having 1 to 6 carbon atoms and at least one of said radicals is vselected `from the class-consisting of primary and secondary radicals, which process comprises passing said' disulfide, agas containing free oxygen, water in an amount between about 1 and about 20 weight percent based on said disulfide, and a catalytic quantity of a nitrogen oxide selected from the group consisting of NO, N02, N203, N204 and N205, downwardly in concurrent contact through a vertical reaction zone at a temperature between about 20 F. and about F.,.and continuing the oxidation until more than 90 percent by weight of said disulfide has been oxidized.

WAYNE A. PROELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,433,395 Proell 81 Shoemaker Dec. 30, 1947 Proell Dec. 30, 1947 

